Dissolution of a particle system at the fluid/fluid interface

Abstract

Dissolution behaviour of a particle system (acetaminophen) at a liquid paraffin/water interface is investigated under conditions of natural convection. Mass flow, the number of particles present in steady-state and their size during dissolution have been measured. Theoretically the minimum and maximum number of particles that can be present at an interface, is derived. Experimentally it was found that the actual number of particles present at the interface is within these extreme values. Dissolution via the pores in between the particles, causes a particle size distribution in steady state, ranging from the initial size of the particle to zero. A particle freshly substituted into the dissolving layer is having its initial maximum size, occupying an area (s 0) of the interface. Multiplying the counted number of particles in steady state with the area s 0, a value is found that is equal to the total available interfacial area, as if a tablet is dissolving with zero porosity. It is shown in this study that this is the result of a limit on number of dissolving particles that can be present at an interface.